Recording medium, recording method, recording device, and reproduction method and reproducer

ABSTRACT

A recording medium has a first area in which data encoded with a first error correction code is recorded and a second area in which data encoded with the first error correction code and data decodable with a second error correction code that is different from the first error correction code are mixedly recorded. Data that causes the cumulated value of a DC component per unit period of data reproduced from the second area to deviate is recorded in the second area.

TECHNICAL FIELD

The present invention relates to a recording medium, a recording method,a recording apparatus, a reproducing method, and a reproducing apparatusfor digital data.

BACKGROUND ART

Since CDs (Compact Discs) are easy to produce, inexpensive, and easy tohandle, they have widespread as mediums for storing various types ofdata such as digital audio data and video data, computer programs, andso forth.

In recent years, as the performance of personal computers has beenimproved and a CD-R (CD-Recordable) disc and a CD-RW (CD-Rewritable)disc have come out, digital data recorded on for example a CD-DA(CD-Digital Audio) disc can be easily copied. This copying operation isillegal because it disregards copyright of the digital data. Thus, it isnecessary to protect copyright of digital data recorded on the CD.

From such a point of view, as new mediums, a DVD-Audio (DigitalVersatile Disc-Audio) disc, an SACD (Super Audio CD) disc, and so forthhave been standardized so that permission or prohibition for their copyoperations can be designated. However, since the formats of theDVD-Audio disc and SACD disc are not compatible with the format of theCD, the new mediums require their dedicated drive devices. They preventthese discs to become widespread.

Thus, a recording medium, a recording method or a reproducing method,and a recording apparatus or a reproducing apparatus that providesecurity, namely a copyright protecting function while havingcompatibility with a conventional drive device are desired. However, ifthese mediums have compatibility with a conventional drive device, theircopyright protection function will not work. Thus, data that is readfrom such a recording medium can be directly copied to a CD-R disc or aCD-RW disc.

In addition, there is a need to read a part of data from for example aDDCD (Double Density CD) on which the data has been recorded with ECC(Error Checking and correcting Code) using a conventional CD drivedevice. However, the need has not been satisfied from a view point ofcopyright protection.

From the foregoing point of view, the present invention provides a CDthat has high compatibility with a conventional CD and prevents itscontents from being illegally copied. In the following description, itis assumed that a CD includes a CD-DA and a CD-ROM.

DISCLOSURE OF THE INVENTION

Claim 1 of the present invention is a recording medium having a firstarea on which data that has been encoded with a first error correctioncode is recorded; and a second area on which data that has been encodedwith the first error correction code and data that is decodable with asecond error correction code that is different from the first errorcorrection code are mixedly recorded, wherein data that causes thecumulated value of a DC component per unit period of the data reproducedfrom the second area to deviate is recorded in the second area.

Claim 7 of the present invention is a recording method, comprising thesteps of recording data that has been encoded with a first errorcorrection code to a first area of a recording medium; mixedly recordingdata that has been encoded with the first error correction code and datathat is decodable with a second error correction code that is differentfrom the first error correction code to a second area of the recordingmedium; and recording data that causes the cumulated value of a DCcomponent per unit period of the data reproduced from the second area todeviate to the second area.

Claim 13 of the present invention is a recording apparatus, comprising afirst encoding process portion for performing an encoding processincluding an error correction code encoding process for data that isinput with a first error correction code; a second encoding processportion for performing a second encoding process including an errorcorrection code encoding process with a second error correction codethat is different from the first error correction code; a modulatingprocess portion for receiving output data of the first encoding processportion and output data of the second encoding process portion,performing a modulating process for the output data of the firstencoding process portion and the output data of the second encodingprocess portion, and performing a modulating process for modulating theoutput data of the second encoding process portion so that data thatcauses the cumulated value of a DC component per unit period of theoutput data of the second encoding process portion to deviate iscontained in the output data of the second encoding process portion; anda recording portion for receiving output data of the modulating processportion and mixedly recording data encoded with the first errorcorrection code and data decodable with the second error correctioncode, which is different from the first error correction code.

Claim 20 of the present invention is a reproducing apparatus, comprisinga head portion for reading data from a recording medium having a firstarea on which data that has been encoded with a first error correctioncode is recorded and a second area on which data that has been encodedwith the first error correction code and data that is decodable with asecond error correction code that is different from the first errorcorrection code are mixedly recorded, wherein data that causes thecumulated value of a DC component per unit period of the data reproducedfrom the second area to deviate is recorded in the second area; adecoding process portion for performing a decoding process for data thathas been read from the head portion; an error correcting process portionfor performing an error correcting process for output data of thedecoding process portion with the first error correction code; agenerating portion for decrypting key data in accordance with a processresult of the error correcting process portion; and a decrypting portionfor decrypting encrypted data that has been read from the first area andthat has been output from the decoding process portion with the key datadecrypted by the generating portion.

Claim 23 of the present invention is a reproducing method, comprisingthe steps of reading data from a recording medium having a first area onwhich data that has been encoded with a first error correction code isrecorded and a second area on which data that has been encoded with thefirst error correction code and data that is decodable with a seconderror correction code that is different from the first error correctioncode are mixedly recorded, wherein data that causes the cumulated valueof a DC component per unit period of the data reproduced from the secondarea to deviate is recorded in the second area; performing a decodingprocess for data that has been read; performing an error correctingprocess for the decoded data with the first error correction code;decrypting key data in accordance with a process result of the errorcorrecting process; and decrypting encrypted data that has been readfrom the first area with the decrypted key data.

According to the present invention, a recording medium has a first areaon which data encoded with a first error correction code is recorded anda second area on which data encoded with a second error correction codeand data that can be decrypted with a second error correction code thatis different from the first error correction code are mixedly recorded.Data that causes the cumulated value of a DC component per unit periodof data that is reproduced to deviate is recorded in the second area. Asa result, a decoding process for data recorded on the recording mediumcan be selectively performed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a systematic diagram describing the present invention.

FIG. 2 is a systematic diagram describing the present invention.

FIG. 3 is a systematic diagram describing the present invention.

FIG. 4 is a systematic diagram describing the present invention.

FIG. 5 is a schematic diagram showing a data arrangement describing thepresent invention.

FIG. 6 is a schematic diagram showing the data arrangement describingthe present invention.

FIG. 7 is a schematic diagram showing the data arrangement describingthe present invention.

FIG. 8 is a schematic diagram showing the data arrangement describingthe present invention.

FIG. 9 is a schematic diagram showing the data arrangement describingthe present invention.

FIG. 10 is a schematic diagram showing the data arrangement describingthe present invention.

FIG. 11A to FIG. 11E are schematic diagrams describing a DSV processaccording to the present invention.

FIG. 12A to FIG. 12D are schematic diagrams describing an errorcorrecting process according to the present invention.

FIG. 13A to FIG. 13D are schematic diagrams describing the structure andoperation of an optical disc according to the present invention.

FIG. 14 is a block diagram showing a recording apparatus according to anembodiment of the present invention.

FIG. 15 is a block diagram showing a reproducing apparatus according tothe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, with reference to the accompanying drawings, a recording medium, arecording apparatus, and a reproducing apparatus according to thepresent invention will be described. First of all, a structure that is apremise of the present invention will be described.

(1) Error Correction Code of CD

An error correction code used in the current CD standard is called CIRC(Cross Interleaved Read-Solomon Code). In the CIRC error correctioncode, two Reed-Solomon code sequences referred to as C1 and C2 whoseminimum distance is 5 are used.

FIG. 1 shows a CIRC encoder circuit 10 used in a recording apparatus fora CD. In a CD, six successive samples L0 to L5 of digital audio data onthe left channel and six successive samples R0 to R5 of digital audiodata on the right channel compose one frame. Each of the data L0 to L5and R0 to R5 is composed of 16 bits. The data L0 to L5 and R0 to R5 aredivided into high order eight bits D0A to D11A and low order eight bitsD0B to D11B. Each of eight bit blocks D0A to D11B are called a symbol.

The symbols D0A to D11B are supplied to a delaying and scramblingcircuit 11. The delaying and scrambling circuit 11 delays symbols ofeven-numbered samples by two symbols. In addition, the delaying andscrambling circuit 11 scrambles all the symbols. outputs of the delayingand scrambling circuit 11 are supplied to a C2 encoder circuit 12. TheC2 encoder circuit 12 encodes the scrambled symbols with (28, 24, 5)Reed-Solomon codes on GF (2⁸) and generates four-symbol Q parities Q0 toQ3. Outputs of the C2 encoder circuit 12 are supplied to an interleavingcircuit 13. Assuming that a unit delay amount is denoted by D, symbolsare delayed by delay amounts 0, D, 2D, . . . , 27D that are different inarithmetic progression. The current CD standard prescribes D=4 frames.Adjacent symbols are spaced apart by four frames each. In the followingdescription, a CIRC system with D=4 is referred to as “CIRC4 system”.

Thereafter, outputs of the interleaving circuit 13 are supplied to a C1encoder circuit 14. The C1 encoder circuit 14 encodes the symbols with(32, 28, 5) Reed-Solomon codes on GF (2⁸). As a result, the C1 encodercircuit 14 generates four-symbol P parities P0 to P3. The outputs of theC1 encoder circuit 14 are also supplied to a delaying circuit 15. Thedelaying circuit 15 alternately delays symbols by one symbol. Inaddition, an inverter circuit 16 inverts the Q parities Q0 to Q3 and Pparities P0 to P3. Outputs of the inverter circuit 16 are supplied as anencoded signal of the encoder circuit 10. The encoded signal is suppliedto an EFM modulating circuit. An EFM modulated signal is recorded on arecordable optical disc or an original with which CDs are produced.

FIG. 2 shows a CIRC decoder circuit 20 used in a reproducing apparatus.The decoder circuit 20 performs a complementary process of the encodercircuit 10. In other words, an EFM demodulating circuit demodulates anEFM modulated signal reproduced from an optical disc, in this example aCD, and outputs an original data sequence (encoded signal). The encodedsignal that is an output signal of the EFM demodulating circuit issupplied to a delaying circuit 21. The delaying circuit 21 delayssymbols that have not been delayed by the delaying circuit 15 of theencoder circuit 10 by one symbol each. As a result, the delaying circuit21 relatively cancels the delays of the symbols made by the delayingcircuit 15. In addition, an inverter circuit 22 re-inverts the symbolsthat have been inverted by the inverter circuit 16 of the encodercircuit 10. As a result, the encoded outputs of the C1 encoder circuit14 are obtained.

A C1 decoder circuit 23 decodes the encoded outputs and outputs theoriginal symbols. The decoded symbols are supplied to a deinterleavingcircuit 24. The deinterleaving circuit 24 delays the symbols by delayamounts 27D, 26D, . . . , D, and 0 that are different in arithmeticprogression. As a result, the deinterleaving circuit 24 relativelycancels the delays of the symbols made by the interleaving circuit 13 ofthe encoder circuit 10. At that point, the delay amount D is 4.

Thereafter, outputs of the deinterleaving circuit 24 are supplied to aC2 decoder circuit 25. The C2 decoder circuit 25 decodes the outputsymbols of the deinterleaving circuit 24 and outputs the originalsymbols. The decoded symbols are supplied to a delaying and descramblingcircuit 26. The delaying and descrambling circuit 26 descrambles all thesymbols. In addition, the delaying and descrambling circuit 26 delayssymbols of the odd-numbered samples by two symbols and outputs theoriginal audio data L0 to R5 (symbols D0A to D11B). The foregoingprocess is executed for each frame. As a result, the original digitalaudio data is successively obtained. Thereafter, the digital audio datais converted into analog data and the original analog audio signals ofleft and right channels are obtained.

At that point, error flags are extracted from the C1 decoder circuit 23and the C2 decoder circuit 25. The error flags are supplied to aninterpolation flag generating circuit 27. The interpolation flaggenerating circuit 27 generates an error interpolation flag with theerror flags. The interpolation flag causes erroneous data to beinterpolated by an interpolating process such as pre-hold interpolationor average value interpolation.

The foregoing process is the CIRC4 error correcting process prescribedin the current CD standard. The DDCD standard and so forth prescribe anencoding system called CIRC7 system that uses an error correction code.

The encoder circuits 12 and 14 and the decoder circuits 23 and 25according to the CIRC4 system are the same as those according to theCIRC7 system. However, the delay amount D of each of the interleavingcircuit 13 and the deinterleaving circuit 24 in the CIRC7 system isseven frames (four frames in the CIRC4 system).

Thus, the interleave length in the CIRC7 system is larger than that inthe CIRC4 system, the CIRC7 system has higher correction performancethan the CIRC4 system against a burst error (that continues in data thatis read from a CD as an optical disc due to a finger print adheredthereon or a scratch on a reading side thereof). Regardless of values ofthe original data L0 to R5, the C1 sequence in the CIRC4 system is thesame as that in the CIRC7 system, whereas the C2 sequence in the CIRC4system is different from that in the CIRC7 system.

Since the interleave length in the CIRC4 system is different from thatin the CIRC7 system, when data is recorded on a CD as an optical disc inaccordance with the CIRC4 system, a reproducing apparatus in accordancewith the CIRC7 system cannot decode the data (namely, the apparatuscannot reproduce the data from the CD). Likewise, when data is recordedon an optical disc in accordance with the CIRC7 system, a reproducingapparatus in accordance with the CIRC4 system cannot decode the datafrom the disc (namely, the apparatus cannot reproduce the data from thedisc).

However, when the original data L0 to R5 are arranged in a predeterminedmanner, regardless of whether data has been encoded in accordance withthe CIRC4 error correcting system or the CIRC7 error correcting system,the data can be normally decoded.

FIG. 3 and FIG. 4 are schematic diagrams describing arrangements of datathat can be decoded regardless of the CIRC4 system or the CIRC7 system.In this example, data is encoded in accordance with the CIRC7 system.The encoded data is recorded on an optical disc. The encoded datarecorded on the optical disc is decoded in accordance with the CIRC4system.

FIG. 3 shows an encoder circuit 10S in accordance with the CIRC7 system.The encoder circuit 10S has the same structure as the encoder circuit 10described with FIG. 1. However, the interleaving circuit 13 of theencoder circuit 10S has a delay amount D of 7. FIG. 4 shows a decodercircuit 20F in accordance with the CIRC4 system. The decoder circuit 20Fhas the same structure as the decoder circuit 20 in accordance with theCIRC4 system. However, the deinterleaving circuit 24 of the decodercircuit 20F has a delay amount D of 4. A CD as an optical disc isinterposed between the encoder circuit 10S in accordance with the CIRC7system and the decoder circuit 20F in accordance with the CIRC4 system(in FIG. 3 and FIG. 4, one CD is shown in common; an EFM modulatingcircuit and an EFM demodulating circuit are omitted).

In FIG. 3 and FIG. 4, numerals represent offset amounts of individualframes. When a C2 decoder circuit 25 of the decoder circuit 20 outputsdata S1 to S24 as outputs D0A to D1B, the offset amount (frame number)of a frame that contains the data S1 to S24 is called reference value 0.As a result, when the data S1 to S24 are output from the C1 decodercircuit 23, offset amounts are designated −108 , −104, −100, . . . and 0in accordance with delay times of the deinterleaving circuit 24.

Since delaying circuits 13 and 21 are disposed, the offset amounts forwhich the data S1 to S24 are output from the interleaving circuit 13 are−109, −105, −101, . . . , and so forth. The offset amounts for which thedata S1 to S24 are output from the delaying and scrambling circuit 11are −109, −112, −115, . . . , and −190 due to delay times of theinterleaving circuit 13. Thus, the offset amounts for which the data S1to S24 are input to the encoder circuit 10S are −111, −114, −129, . . ., and −190 due to the delaying and scrambling circuit 11.

Thus, when the data S1 to S24 are arranged for −190th to −111st framesas shown in FIG. 5 to FIG. 6 (data shown in FIG. 5 is followed by datashown in FIG. 6), the C2 decoder circuit 25 simultaneously outputs thedata S1 to S24 as the current frame (0th frame). In FIG. 5 and FIG. 6,since blank data is not contained in the current frame, the blank datamay be any data.

However, in reality, it should be noted that the Q parities Q0 to Q3 andthe P parities P0 to P3 are added to the data S1 to S24, recorded, andreproduced and that these parities are dispersed to the data S1 throughS24. When the data S1 to S24 are arranged to the −156th to −145th framesas shown in FIG. 7 and FIG. 8 (data shown in FIG. 8 is preceded by datashown in FIG. 7), the C2 decoder circuit 25 simultaneously outputs thedata S1 to S24 as the current frame.

Thus, when the data S1 to S24 are arranged to the −190th to −111th frameas shown in FIG. 5 to FIG. 8, they are encoded in accordance with theCIRC7 system, and they are decoded in accordance with the CIRC4 system,then the C2 decoder circuit 25 simultaneously outputs the data S1 to S24as the current frame. At that point, the error flag is not set.

The data S1 to S24 can be normally decoded and reproduced even inaccordance with the CIRC7 system. The data S1 to S24 may have anyvalues. In addition, the data S1 to S24 can be placed in any region ofdata that has been encoded in accordance with the CIRC7 system. In thefollowing description, data or data arrangement like the data S1 to S24that can be normally decoded in accordance with any of the CIRC4 systemand the CIRC7 system is referred to as “special data”.

The data S1 to S24 that are simultaneously output from the C2 decodercircuit 25 are delayed by the delaying and descrambling circuit 26 andare output from the decoder circuit 20F. Thus, as shown in FIG. 9 andFIG. 10 (data shown in FIG. 10 is preceded by data shown in FIG. 9), thedecoder circuit 20F outputs the data S1 to S24 contained in the currentframe (0th frame) and the second frame.

(2) DSV of CD

As shown in FIG. 11A, when the value of a symbol (original data) is forexample 92h (where h represents hexadecimal notation), if the symbol isencoded in accordance with the CIRC7 system and the encoded symbol isconverted into an EFM modulated signal, the channel bits (EFM modulatedsignal) are arranged as shown in FIG. 11B in accordance with conversionand modulation section in the CD standard. Connection bits or marginbits are inserted into a boundary of symbols.

The connection bits are inserted into the boundary so that the minimumduration Tmin of the channel bits becomes long and the maximum durationTmax becomes short. In reality, the connection bits are inserted intothe boundary so that two or more “0's” or “1's” are successive, but notmore than 12 “0's” or “1's” are successive. Thus, the connection bitsare any one of four types of bit patterns shown in FIG. 11C. In thiscase, a pattern “000” is selected in accordance with the foregoingcondition.

Thus, in this case, the channel bits are represented as a bit pattern asshown in FIG. 1D. A cumulated value of a DC component per unit time,namely DSV (Digital Sum Variation), is obtained as shown in FIG. 11E.When one symbol has ended, the DSV increases by “3”. When a symbol isregular digital audio data or the like, the sign and value of the DSVper symbol deviates. In addition, connection bits are selected so thatthe DSV converges at “0”. Thus, the DSV converges in a predeterminedrange close to “0”.

However, when for example symbols 92h are repeated in any method, theDSV increases by 3 per symbol. When the DSV increases (or decreases) anddeviates from a predetermined range, the DSV affects asymmetrycompensation of the reproducing circuit of a CD as an optical disc.Thus, data cannot be correctly reproduced from the CD.

(3) Structure According to Present Invention

FIG. 12A is an enlarged view showing a part of a track of an opticaldisc as a recording medium according to the present invention. The partof the track is divided into a plurality of areas. Any data that isencoded in accordance with the CIRC7 system is recorded in areas P7 thatare alternative areas of the divided areas. Special data that can benormally decoded in accordance with any of the CIRC4 system and theCIRC7 system is recorded. in other alternative areas P47 of the dividedareas. At least last data (symbol) of the special data is for examplethe foregoing value 92h. In other words, the DSV of the data itselflargely deviates from “0”. On the start side (not shown) of the track,other regular data, for example digital audio data, has been is encodedin accordance with the CIRC4 system and recorded.

When a dedicated reproducing apparatus (that will be described later)reproduces data from an optical disc having such a track, the apparatuscan normally decode the data in the areas P7 and P47 and outputsreproduced data. In addition, the apparatus can normally reproduce dataof the other areas in which data has been encoded in accordance with theCIRC4 system.

Next, with a conventional reproducing apparatus and a conventionalrecording apparatus, namely a reproducing apparatus or a recordingapparatus in accordance with only the CIRC4 system, the case of whichdata that is read from an optical disc having the track shown in FIG.12A is copied will be considered. The conventional reproducing apparatusand recording apparatus accord with only the CIRC4 system. Thus, whenthe conventional reproducing apparatus reads data from the track shownin FIG. 12A of the optical disc and decodes the data, since the data hasbeen encoded in accordance with the CIRC7 system and recorded in thearea P7, if the data of the area P7 is decoded, as shown in FIG. 12B,the error flag becomes “1”. However, in the area P47, since the specialdata has been recorded, it can be also normally decoded in accordancewith the CIRC4 system. Thus, the error flag is not set. In other words,the value of the error flag is varied as shown in FIG. 12B in accordancewith the CIRC systems of data in the areas P7 and P47.

Thus, the conventional reproducing apparatus outputs data as shown inFIG. 12C. In other words, while a signal is being read from the areaP47, the special data in the area P47 is normally decoded and output. Incontrast, while data is being read from the area P7, data that has beenencoded in accordance with the CIRC7 system cannot be decoded. Becauseof an error, an interpolated value is output. If data is interpolated inaccordance with the pre-hold interpolating method, the immediatelypreceding normal value, namely the last value that has been normallydecoded from the special data of the area P47, in this case, the value92h is output. While a signal is being read from the area P7, the values92h are successively output as interpolated values or interpolated data.In the EFM modulating system, connection bits of three bits are insertedinto a boundary between two adjacent data symbols. With the connectionbits properly selected, the DSV is controlled.

Reproduction output data shown in FIG. 12C is copied to a recordableoptical disc such as a CD-R disc. As a result, when data is reproducedfrom a copied optical disc, the DSV varies in the areas P7 and P47 asshown in FIG. 12D. In other words, since data has been normally copiedin the area P47 of the optical disc, the DSV does not largely increaseor decrease. However, since the data in the area P7 is a sequence of forexample values 92h, only particular connection bits can be selected.Thus, the DSV cannot be controlled so that it approaches 0. As a result,the DSV simply increases for each data symbol.

When the DSV increases while data in the area P7 is being demodulated,the DSV deviates from a predetermined range. As a result, data copied asshown in FIG. 12C cannot be reproduced. In other words, data cannot besubstantially copied to a recordable optical disc.

Since the appearance of an original optical disc is very similar to theappearance of a copied optical disc, it is difficult to distinguish themwith their appearances. However, when data in the area P47 is decoded inaccordance with the CIRC4 system and the CIRC7 system, it can bedetermined whether the optical disc is an original optical disc or acopied optical disc with the decoded result.

(4) Optical Disc According to Present Invention

FIG. 13A shows an example of an optical disc according to the presentinvention. FIG. 13A shows an enlarged track on an optical disc accordingto the present invention. On the optical disc according to the presentinvention (hereinafter simply referred to as optical disc), a firstlead-in area L1, a first main data area PA1, and a first lead-out areaLO1 are successively formed in a concentric circular shape from theinner periphery side to the outer periphery side. On the outer peripheryside of the first lead-out area LO1, a second lead-in area LI2, a secondmain data area PA2, and a second lead-out area LO2 are successively andoutwardly formed in a concentric circular shape. Tracks are spirally andsuccessively formed from the first lead-in area LI1 to the secondlead-out area LO2.

In the first lead-in area LI1, the first main data area PA1, and thefirst lead-out area LO1, data is recorded in accordance with for examplethe CD-DA standard. In the first main data area PA1, as main data,digital audio data that has been encoded with an error correction codein accordance with the CD-DA standard like a conventional CD isrecorded.

In the second lead-in area LI2, the second main data area P2, and thesecond lead-out area LO2, digital audio data that has been encrypted andcompressed is recorded. As shown in FIG. 13A, the second main data areaPA2 is divided into four areas PA21 to PA24.

In the third divided area PA23 of the second main data area PA2, digitalaudio data that has been compressed in accordance with for example MP-3(MPEG-1 Audio Layer 3) system or ATRAC (Adaptive Transform AcousticCoding: registered trademark), encrypted, and encoded in accordance withthe CIRC4 system is recorded. In the first divided area PA21 of thesecond main data area PA, a decrypting program that decrypts digitalaudio data recorded in the third divided area PA23, decompresses thedecoded data, and obtains original digital audio data, namely data ofso-called reproducing software, that has been encoded in accordance withthe CIRC4 system is recorded.

In the second divided area PA22 of the second main data area PA2, keydata K22 with which the encrypted digital audio data recorded in thethird divided area PA23 is decrypted is encrypted with key data K24 thatwill be described later and that has encoded in accordance with theCIRC4 system is recorded. In the fourth divided area PA24 of the secondmain data area PA2, key data K24 with which the key data K22 recorded inthe second divided area PA22 is decrypted is recorded.

As shown in FIG. 13B, the fourth divided area PA24 is also divided intoa plurality of areas. In an area P47 of the divided areas, the key dataK24 or dummy data is recorded as the special data described in section(1). In an area P7 of the divided areas, data that has been encoded inaccordance with the CIRC7 system is recorded so that when the data isdecoded in accordance with the CIRC4 system, an error takes place. Inother words, the last symbol of the key data K24 or dummy data recordedin the area P47 is “92h”.

When the data in the fourth divided area PA24 is decoded in accordancewith the CIRC4 system, since the key data K24 or dummy data has beenrecorded as the special data in the area P47, the key data K24 or dummydata recorded in the area P47 can be normally decoded. Thus, as shown inFIG. 13C, the error flag is not set. However, since data recorded in thearea P7 has been encoded in accordance with the CIRC7 system, when thedata is decoded in accordance with the CIRC4 system, an error takesplace. Thus, as shown in FIG. 13C, the error flag is set.

In other words, as shown in FIG. 13C, the error flag varies inaccordance with the CIRC system of the data recorded in the forth areaPA24. The error flag values “0” and “1” can be freely set depending onwhether data is recorded as the special data that can be decoded inaccordance with any of the CIRC4 system and the CIRC7 system or as datathat is encoded in accordance with the CIRC7 system. In other words, toset the error flag to 0, the key data K24 and dummy data are recorded asthe special data. To set the error flag to 1, any data is encoded inaccordance with the CIRC7 system and recorded.

According to the present invention, the arrangement pattern of the errorflag values “0” and “1” is a part of the key data K24. The areas P7 andP47 are formed so that the arrangement pattern of the error flag values“0” and “1” and the key data recorded in the area P47 compose the keydata K24.

The standard about physical dimensions and characteristics such thediameter and thickness of the optical disc is based on the currentstandard of the CD.

On the optical disc formed in the foregoing manner, data recorded in thefirst main data area PA1 can be reproduced as digital audio data by aconventional reproducing apparatus in accordance with the CIRC4 system,namely a CD player, a CD-ROM drive device, or the like.

Data recorded in the second main data area PA2 can be reproduced by adedicated reproducing apparatus that will be described later. In thiscase, key data K24 is generated or decrypted with an error flag of whichdata recorded in the fourth area PA24 is decoded, for example data inaccordance with an error flag shown in FIG. 13C, and key data read fromthe area P47. With the decrypted key data K24, the key data K22 recordedin the second divided area PA22 can be decrypted. Thus, with thedecrypted key data K22 and data of the reproducing program that is readfrom the first divided area PA21, digital audio data in the thirddivided area PA23 can be decrypted and decompressed. As a result,original digital audio data, namely non-encrypted digital audio data,can be obtained from the data that is read from the second main dataarea PA2 of the optical disc.

On the other hand, even if data recorded on the optical disc shown inFIG. 13A is tried to be copied, as described in section (3), the datacannot be substantially copied.

Even if data recorded on the optical disc shown in FIG. 13A can becopied to a recordable optical disc, for example a CD-R disc, as shownin FIG. 13D, since the last symbol of the special data of the area P47of the second main data area PA2 of the recordable optical disc as acopied disc is “92h”, an error that will take place in the area P7 isinterpolated and data of “92h” is recorded as a decoded result of datathat is read from the area P7. In other words, as shown in FIG. 13D,data that can be decoded in accordance with the CIRC4 system is recordedto an optical disc as a copied disc.

Thus, even if data recorded on a copied optical disc is decoded inaccordance with the CIRC4 system, data about the error flag that variesas shown in FIG. 13C cannot be obtained. Thus, a part of the key dataK24 cannot be obtained. As a result, since the key data K24 cannot beobtained, the key data K22 cannot be decrypted. Consequently, thedigital audio data recorded in the third divided area PA23 cannot bedecrypted. Thus, the digital audio data recorded in the second main dataarea PA2 cannot be substantially copied. At that point, as describedabove, when data in the fourth divided area PA24 is being decoded orreproduced, the DSV increases. As a result, data cannot be reproducedfrom a copied optical disc. Even if data can be reproduced from theoptical disc, as described above, the key data K24 cannot be obtained.

(5) Recording Apparatus of Present Invention

FIG. 14 shows an example of a recording apparatus for the optical discaccording to the present invention described in section (4). In otherwords, when data is recorded in the first main data area PA1, a systemcontrolling circuit 45 causes switch circuits 32 and 35 to be connectedto terminals 32 a and 35 a as shown in FIG. 14, respectively. Main datasuch as digital audio data is supplied to a CIRC4 encoder circuit 34through an input terminal 31 and the switch circuit 32. The CIRC4encoder circuit 34 performs an encoding process for the main data inaccordance with the CIRC4 system. Output data of the encoded output ofthe CIRC4 encoder circuit 34 is supplied to a sub code encoder circuit37 through the switch circuit 35.

Sub code data is supplied from the controlling circuit 45 to the subcode encoder circuit 37. In this case, the sub code data containsinformation that represents the positions of the first divided area PA21to the fourth divided area PA24 shown in FIG. 13A, for example addressinformation thereof. In such a manner, the sub code encoder circuit 37outputs encoded data to which a sub code is output.

The encoded data is supplied to an EFM modulating circuit 38. The EFMmodulating circuit 38 outputs an EFM modulated signal (channel bits).The signal is supplied to a recording optical head 41 through arecording amplifier 39. The recording optical head 41 records the signalas spiral tracks in the first main data area PA1 of a recordable opticaldisc or an original (simply referred to as optical disc) 50. At thatpoint, the optical disc 50 is rotated at a predetermined linear velocityby a spindle motor 42. In addition, a servo circuit 43 performs varioustypes of servo controls for a recording operation such as focus servo,tracking servo, and servo for record current supplied to the opticalhead 41.

As described in section (4) and FIG. 13A, main data is encoded inaccordance with the CIRC4 system and recorded in the first main dataarea PA1 of the optical disc 50.

When data is recorded in the second main data area PA2, data about thereproducing software is supplied to the CIRC4 encoder circuit 34 throughthe input terminal 31 and the switch circuit 32. The CIRC4 encodercircuit 34 performs an encoding process for the data in accordance withthe CIRC4 system. Output data as encoded output of the CIRC4 encodercircuit 34 is supplied to the EFM modulating circuit 38 through theswitch circuit 35 and the sub code encoder circuit 37. An EFM modulatedsignal that is output from the EFM modulating circuit 38 is supplied tothe optical head 41 through the recording amplifier 39. The optical head41 records the signal in the first divided area PA21 of the second maindata area PA2.

Thereafter, the controlling circuit 45 outputs the key data K22encrypted with the key data K24. The key data K22 is supplied to theCIRC4 encoder circuit 34. The CIRC4 encoder circuit 34 performs anencoding process for the key data K22 in accordance with the CIRC4system. Output data as an encoded output of the CIRC4 encoder circuit 34is supplied to the EFM modulating circuit 38 through the switch circuit35 and the sub code encoder circuit 37. The EFM modulated signal that isoutput from the EFM modulating circuit 38 is supplied to the opticalhead 41. The optical head 41 records the EFM modulated signal in thesecond divided area PA22 of the second main data area PA2.

In addition, the controlling circuit 45 causes the switch circuit 32 tobe connected to the terminal 32 b. In addition, the key data K22 issupplied from the controlling circuit 45 to an encrypting circuit 33.Main data such as digital audio data that has been compressed inaccordance with the foregoing system is supplied to the encryptingcircuit 33 through the input terminal 31. The encrypting circuit 33encrypts the main data with the key data K22. Output data of theencrypting circuit 33 is supplied to the CIRC4 encoder circuit 34through the switch circuit 32. The CIRC4 encoder circuit 34 performs anencoding process for the data in accordance with the CIRC4 system.Output data as an encoded output of the CIRC4 encoder circuit 34 issupplied to the EFM modulating circuit 38 through the switch circuit 35and the sub code encoder circuit 37. An EFM modulated signal that isoutput from the EFM modulating circuit 38 is supplied to the opticalhead 41. The recording optical head 41 records the EFM modulated signalin the third divided area P23 of the second main area data area PA2.

The key data K24, the dummy data, and the data for the area P7 aresupplied from the controlling circuit 45 to an encoder circuit 36 inpredetermined length S and a predetermined order. The encoder circuit 36performs an encoding process for the data as the special data or inaccordance with the CIRC7 system. Output data as an encoded output ofthe encoder circuit 36 is supplied to the EFM modulating circuit 38through the switch circuit 35 and the sub code encoder circuit 37. Atthat point, the modulating circuit 38 modules the output data of theencoder circuit 36 so that the last data symbol of the key data or dummydata recorded in the area P47 shown in FIG. 13 becomes “92 h”. An EFMmodulated signal that is output from the EFM modulating circuit 38 issupplied to the optical head 41. The recording optical head 41 recordsthe EFM modulated signal in the fourth divided area P24 of the secondmain area data area PA2 as shown in FIG. 13B and C. Sub code datarecorded in the second main data area P24 contains information thatrepresents the position of the fourth divided area P24, for exampleaddress information thereof. The switch circuit 35 is connected to theterminal 35 b with a control signal supplied from the controllingcircuit 45.

In the foregoing manner, data is recorded on the optical disc 50. Thus,as described in section (4) and FIG. 13A to FIG. 13B, main data, keydata, special data, and so forth are recorded in respective areas. Whenthe optical disc 50 is an original, with the original on which data hasbeen recorded, namely that has been exposed, a stamper is produced. Withthe stamper, a disc substrate is formed by an injection forming methodor the like. A reflection film made of Al or the like is coated on adisc substrate. As a result, a read-only optical disc can be produced.

(6) Reproducing Apparatus According to Present Invention

FIG. 15 shows an example of a reproducing apparatus that reproduces datafrom the optical disc 50 on which the data has been recorded by therecording apparatus described in section (5). In this case, areproducing optical head 71 reads data from the optical disc 50. Aspindle motor 62 rotates the optical disc 50 at a predetermined linearvelocity. A servo circuit 63 controls various types of servo controlsfor a reproducing operation such as focus servo and tracking servo forthe optical disc 50.

When data is reproduced from the first main data area PA1 of the opticaldisc 50, an output signal of the optical head 61 is supplied to an EFMdemodulating circuit 72 through a reproducing amplifier 71. The EFMdemodulating circuit 72 performs a demodulating process for the outputsignal of the optical head 61. An output signal of the EFM demodulatingcircuit 72 is supplied to a CIRC4 decoder circuit 73. The CIRC4 decodercircuit 73 performs a decoding process, namely an error detectingprocess and an error correcting process, for the output signal of theEFM demodulating circuit 72 in accordance with the CIRC4 system. Digitalaudio data is output from the decoder circuit 73. A controlling circuit65 causes a switch circuit 74 to be connected to a terminal 74 a. Afterthe CIRC4 decoder circuit 73 has decoded the digital audio data, thedigital audio data is output to the outside of the apparatus from anoutput terminal 75 through the switch circuit 74.

A part of the demodulated output data of the EFM demodulating circuit 72is supplied to a sub code decoder circuit 78. The sub code decodercircuit 78 extracts sub code data from the part of the demodulatedoutput data. The sub code data is supplied to the system controllingcircuit 65. The controlling circuit 65 obtains information thatrepresents the positions of the first divided area PA21 to the fourthdivided area PA24 of the second main data area PA2, namely addressinformation (FIG. 13A), from the supplied sub code data.

When data is reproduced from the second main data area PA2 of theoptical disc 50, the controlling circuit 65 causes the optical head 61to access the fourth divided area PA24 in accordance with the sub codedata. The optical head 61 reads data from the fourth divided area PA24of the second main data area PA2. The data is supplied to the EFMdemodulating circuit 72. As shown in FIG. 13B, the EFM demodulatingcircuit 72 demodulates the data that has been read from the fourthdivided area PA24 and outputs the demodulated data to the CIRC4 decodercircuit 73.

Thus, data corresponding to the error flag that varies as shown in FIG.13C is output from the CIRC4 decoder circuit 73. Data corresponding tothe error flag is supplied as a part of the key data K24 to thecontrolling circuit 65. The CIRC4 decoder circuit 73 performs a decodingprocess for the data recorded in the area P47 in accordance with theCIRC4 system. The decoded output data is supplied to an extractingcircuit 77. The extracting circuit 77 extracts data of the key data K24from the decoded data. The extracted data is supplied to the controllingcircuit 65. The restores the key data K24 from the decoded data withdata in accordance with both the error flag supplied from the CIRC4decoder circuit 73 and the data extracted by the extracting circuit 77.

Thereafter, the optical head 61 reads data about the reproducingsoftware from the first divided area PA21 of the second main data areaPA2 of the optical disc 50 by the optical head 61. The data issuccessively supplied to the EFM demodulating circuit 72 and the CIRC4decoder circuit 73. As a result, the CIRC4 decoder circuit 73 decodesthe data about the reproducing software and outputs the decoded dataabout the reproducing software. The decoded data about the reproducingsoftware is supplied to a decrypting circuit 76 through the controllingcircuit 65.

In addition, the optical head 61 reads the encrypted key data K22 fromthe second divided area PA22 of the second main data area PA2 of theoptical disc 50. The encrypted key data K22 is successively supplied tothe EFM demodulating circuit 72 and the CIRC7 decoder circuit 77. TheCIRC7 decoder circuit 77 decodes the encrypted key data K22 and outputsthe decoded encrypted key data K22. The decoded encrypted key data K22is supplied to the controlling circuit 65. The controlling circuit 65decrypts the encrypted key data K22 with the key data K24. The decryptedkey data K22 is supplied to a decrypting circuit 76.

The optical head 61 reads data from the third divided area PA23 of thesecond main data area PA2 of the optical disc 50. The data issuccessively supplied to the EFM demodulating circuit 72 and the CIRC4decoder circuit 73. The EFM demodulating circuit 72 and the CIRC4decoder circuit 73 decode the compressed and encrypted digital data. Thedecoded data is supplied to the decrypting circuit 76.

The decrypting circuit 76 decrypts and decompresses the digital datawith the key data K24 and the data about the reproducing softwaresupplied from the controlling circuit 65. As a result, original digitalaudio data is obtained. The controlling circuit 65 causes the data to beoutput to the outside of the apparatus from the output terminal 75through the switch circuit 74 connected to the terminal 74 b.

In such a manner, digital audio data recorded in the first main dataarea PA1 and the second main data area PA2 of the optical disc 50 isoutput as a reproduced output from the output terminal 75.

(7) Others

In the foregoing description, the fourth divided area P24 of the opticaldisc 50 is divided into the area P7 in which data that has been encodedin accordance with the CIRC7 system is recorded and the area P47 inwhich data as the special data is recorded. Alternatively, a whole trackmay be structured as the fourth divided area PA24 in which digital audiodata and so forth are recorded. In the foregoing description, theprocesses for the CIRC4 system and the CIRC7 system described withreference to FIG. 13A to FIG. 15 may be reversed. In addition, as longas interleave lengths of two CIRC system are different, the presentinvention can be applied to other than the CIRC4 system and the CIRC7system. The reproducing order of the first divided area P21 to thefourth divided area P24 shown in FIG. 13A and FIG. 13B can be changed.

In addition, in the foregoing description, as the recording medium, anoptical disc in accordance with the CD standard was exemplified.Alternatively, the recording medium may be a Mini Disc, a DVD, or thelike. Alternatively, data may be transmitted or received through anetwork such as the Internet. When a synchronous pattern is placed atthe beginning of each of the first divided area PA21 to the fourthdivided area PA24, the positions of data that has been read can beaccurately obtained.

1. A recording medium having: a first area on which data that has beenencoded with a first error correction code is recorded; and a secondarea on which data that has been encoded with the first error correctioncode and data that is decodable with a second error correction code thatis different from the first error correction code are mixedly recorded,wherein data that causes the cumulated value of a DC component per unitperiod of the data reproduced from the second area to deviate isrecorded in the second area.
 2. The recording medium as set forth inclaim 1, wherein the data decodable with the second error correctioncode contains the data decodable with the first error correction code,and wherein the data of which the cumulative value of the DC componentdeviates is contained in the data decodable with the first errorcorrection code.
 3. The recording medium as set forth in claim 2,wherein the data recorded in the first area and encoded with the firsterror correction code has been encrypted with at least encryption keydata, and wherein the data decodable with the second error correctioncode composes at least a part of at lest the encryption key data.
 4. Therecording medium as set forth in claim 3, wherein the data decodablewith the first error correction code is placed in the data decodablewith the second error correction code so that when the data decodablewith the second error correction code is decoded with the first errorcorrection code, the data decodable with the first error correction coderepresents a predetermined error pattern in accordance with theencryption key data.
 5. The recording medium as set forth in claim 4,wherein at least part of the data decodable with the first errorcorrection code is dummy data.
 6. The recording medium as set forth inclaim 1, wherein information that represents the position of the secondarea is recorded on the recording medium.
 7. A recording method,comprising the steps of: recording data that has been encoded with afirst error correction code to a first area of a recording medium;mixedly recording data that has been encoded with the first errorcorrection code and data that is decodable with a second errorcorrection code that is different from the first error correction codeto a second area of the recording medium; and recording data that causesthe cumulated value of a DC component per unit period of the datareproduced from the second area to deviate to the second area.
 8. Therecording method as set forth in claim 7, wherein the data decodablewith the second error correction code contains the data decodable withthe first error correction code, and wherein the third recording step isperformed so that the data causing the cumulative value of the DCcomponent to deviate is contained in the data decodable with the firsterror correction code.
 9. The recording method as set forth in claim 8,wherein the first recording step is performed so that the data recordedin the first area and encoded with the first error correction code hasbeen encrypted with at least encryption key data, and wherein the datadecodable with the second error correction code composes at least a partof at lest the encryption key data.
 10. The recording method as setforth in claim 9, wherein the second recording step is performed byplacing the data decodable with the first error correction code in thedata decodable with the second error correction code so that when thedata decodable with the second error correction code is decoded with thefirst error correction code, the data decodable with the first errorcorrection code represents a predetermined error pattern in accordancewith the encryption key data.
 11. The recording method as set forth inclaim 10, wherein at least part of the data decodable with the firsterror correction code is dummy data.
 12. The recording method as setforth in claim 7, further comprising the step of: recording informationthat represents the position of the second area to the recording medium.13. A recording apparatus, comprising: a first encoding process portionfor performing an encoding process including an error correction codeencoding process for data that is input with a first error correctioncode; a second encoding process portion for performing a second encodingprocess including an error correction code encoding process with asecond error correction code that is different from the first errorcorrection code; a modulating process portion for receiving output dataof the first encoding process portion and output data of the secondencoding process portion, performing a modulating process for the outputdata of the first encoding process portion and the output data of thesecond encoding process portion, and performing a modulating process formodulating the output data of the second encoding process portion sothat data that causes the cumulated value of a DC component per unitperiod of the output data of the second encoding process portion todeviate is contained in the output data of the second encoding processportion; and a recording portion for receiving output data of themodulating process portion and mixedly recording data encoded with thefirst error correction code and data decodable with the second errorcorrection code, which is different from the first error correctioncode.
 14. The recording apparatus as set forth in claim 13, wherein thesecond encoding process portion is configured to perform the errorcorrection code encoding process with the second error correction codeand perform an encoding process for data decodable with any of the firsterror correction code and the second error correction code.
 15. Therecording apparatus as set forth in claim 14, wherein the modulatingprocess portion is configured to perform the modulating process so thatthe data decodable with any of the codes supplied from the secondencoding process portion contains the data causing the cumulated valueof the DC component per unit period of the reproduced data to deviate.16. The recording apparatus as set forth in claim 13, furthercomprising: a recording control portion for mixedly recording the dataencoded with the first error correction code and the data decodable withthe second error correction code different from the first errorcorrection code, and wherein the control portion is configured to causethe data decodable with the second error correction code to compose atleast a part of the encryption key data.
 17. The recording apparatus asset forth in claim 16, wherein the recording control portion isconfigured to record the data decodable with any of the codes in thedata decodable with the second error correction code so that when thedata decodable with the second error correction code is decoded with thefirst error correction code, the data decodable with any of the codesrepresents a predetermined error pattern in accordance with theencryption key data.
 18. The recording method as set forth in claim 17,wherein a part of the data decodable with any of the codes is dummydata.
 19. The recording apparatus as set forth in claim 13, whereininformation that represents the position of an area in which the dataencoded with the first error correction code and the data decodable withthe second error correction code different from the first errorcorrection code are mixedly recorded.
 20. A reproducing apparatus,comprising: a head portion for reading data from a recording mediumhaving a first area on which data that has been encoded with a firsterror correction code is recorded and a second area on which data thathas been encoded with the first error correction code and data that isdecodable with a second error correction code that is different from thefirst error correction code are mixedly recorded, wherein data thatcauses the cumulated value of a DC component per unit period of the datareproduced from the second area to deviate is recorded in the secondarea; a decoding process portion for performing a decoding process fordata that has been read from the head portion; an error correctingprocess portion for performing an error correcting process for outputdata of the decoding process portion with the first error correctioncode; a generating portion for decrypting key data in accordance with aprocess result of the error correcting process portion; and a decryptingportion for decrypting encrypted data that has been read from the firstarea and that has been output from the decoding process portion with thekey data decrypted by the generating portion.
 21. The reproducingapparatus as set forth in claim 20, wherein an encrypting process hasbeen performed for the data encoded with the first error correction coderecorded on the recording medium in accordance with the key data,wherein the key data has been recorded on the recording medium, andwherein the generating portion is configured to generate another keydata for which the key data is decrypted with an error pattern decodedwith the first error correction code and decrypt the key data with theother key data.
 22. The reproducing apparatus as set forth in claim 21,wherein information that represents the position of the second area hasbeen recorded on the medium, and wherein the apparatus is configured tocontrol the position of the head portion in accordance with theinformation representing the position so as to read the data of thesecond area.
 23. A reproducing method, comprising the steps of: readingdata from a recording medium having a first area on which data that hasbeen encoded with a first error correction code is recorded and a secondarea on which data that has been encoded with the first error correctioncode and data that is decodable with a second error correction code thatis different from the first error correction code are mixedly recorded,wherein data that causes the cumulated value of a DC component per unitperiod of the data reproduced from the second area to deviate isrecorded in the second area; performing a decoding process for data thathas been read; performing an error correcting process for the decodeddata with the first error correction code; decrypting key data inaccordance with a process result of the error correcting process; anddecrypting encrypted data that has been read from the first area withthe decrypted key data.
 24. The reproducing method as set forth in claim23, wherein an encrypting process has been performed for the dataencoded with the first error correction code recorded on the recordingmedium in accordance with the key data, wherein the key data has beenrecorded on the recording medium, and wherein the decrypting step isperformed by generating another key data for which the key data isdecrypted with an error pattern decoded with the first error correctioncode and decrypting the key data with the other key data.
 25. Thereproducing method as set forth in claim 24, wherein information thatrepresents the position of the second area has been recorded on themedium, and wherein the reproducing method further comprises the stepof: reading the data of the second area in accordance with theinformation representing the position.